John Catsoulis - Designing Embedded Hardware

Welcome to the second edition of Designing Embedded Hardware . In these pages, I hope to give you an understanding of the design process for creating computer hardware. Just as there is beauty in well-written software, there is beauty in well-designed hardware. With embedded computers, you get to understand the machine at all levels, at once aware of currents flowing through circuit traces and software executing complex algorithms. In fact, it is not possible to write embedded software without understanding the hardware, nor is it possible to design hardware without understanding software. You become involved with the machine to a degree beyond that which is possible with desktop computers. Best of all, it's a lot of fun.

In selecting chips and designs for this book, I have tried to choose, where possible, parts that are both trivial to use yet exceptionally useful. I have no connection, financial or otherwise, with any of the companies or businesses mentioned in this book, and I receive no benefits from them. Every component or product included in this book is there based on its own merits. You may notice a prevalence of components from certain manufacturers. This simply reflects my personal preference for using their chips, based on my experience. Such companies produce chips that are easy to use, are reliable and robust, have great technical support, and provide thorough and comprehensive technical data. In other words, they meet all the necessary requirements for inclusion in a book for beginners.

When the first edition of Designing Embedded Hardware was published, I deliberately left out software. There were two reasons for this. First, there are many good books already written on C programming, embedded firmware development in C, porting Linux to embedded systems, coding in Python, writing Java software, and so on. (And of course, the best of these are naturally published by O'Reilly.) The second reason is that assembly language, that most basic of programming tools, is so different from processor to processor that it would not have been possible to cover all the instruction sets of the processors in the book, let alone do them justice. However, I have decided to include some software in this edition. I won't even attempt to cover the instructions of each processor in this book. What I will do is show some simple assembly language techniques. While the instructions may be wildly different between architectures, the basic concepts are the same.

Also new to this book is a chapter on the Forth programming language. Forth is a relatively old language that has faded from the forefront of software development, and as such, it's rare to find a book giving the language good coverage. Forth is a very useful tool for embedded system development to which many engineers have yet to be exposed. The language is the basis of the Open Firmware standard and is used by design engineers at Apple, Sun, and many other manufacturers. It's a useful language to know, and it is worth taking the time to learn.

Many of the designs in this book look easy, and they are. They are intended as simple building blocks, allowing you to mix and match to achieve the embedded systems you need. I hope you will find this book useful. Once you've finished reading it, go and build something!

John Catsoulis

Brisbane, Australia

January 2005

http://www.embedded.com.au

Using Code Examples

This book is here to help you get your job done. In general, you may use the code in this book in your programs and documentation. You do not need to contact O'Reilly for permission unless you're reproducing a significant portion of the code. For example, writing a program that uses several chunks of code from this book does not require permission. Selling or distributing a CD-ROM of examples from O'Reilly books does require permission. Answering a question by citing this book and quoting example code does not require permission. Incorporating a significant amount of example code from this book into your product's documentation does require permission.

We appreciate, but do not require, attribution. An attribution usually includes the title, author, publisher, and ISBN. For example: " Designing Embedded Hardware , by John Catsoulis. Copyright 2005 O'Reilly Media, Inc., 0-596-00755-8."

If you feel your use of code examples falls outside fair use or the permission given above, feel free to contact the publisher at .

Conventions

The conventions used in this book are as follows:

Main text

Source Code

Signal (active high)

(active low)

Hexadecimal numbers are denoted with the prefix 0x , and sometimes with the prefix $ , where appropriate for certain processors.

Binary numbers are denoted by the prefix %.

K is 1,024, while k is 1,000.

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